Sensitivity of Kβ mainline X-ray emission to structural dynamics in iron photosensitizer

Rogvall, Johanna; Singh, Roshan Kumar; Vacher, Morgane; Lundberg, Marcus

doi:10.1039/d2cp05671b

Cited by 5 publications

(3 citation statements)

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“…Thus, quantitative conclusions can be made using the Kβ 1,3 first-moment positions and Kβ 1,3 –Kβ′ energy splitting within a given oxidation and spin state. ,, Great care is therefore required when comparing data with different oxidation and/or spin states, as the nominal oxidation , and the local spin state , seem to be the dominant contributions in the Kβ energy position and splitting.…”

Section: Discussionmentioning

confidence: 99%

“…It is expected that the effect is very small, as the core orbitals are not involved in the orbital mixing with the ligand orbitals. This strategy has been successfully used in the past to reproduce different types of X-ray spectra, including metal L-edge, − K-pre-edge, , RIXS, , and Kα and Kβ XES . The 1s and 3p core-ionized states were calculated with a novel projection technique called the highly excited state (HEXS) ,, that sets the configuration-interaction coefficients of configuration-state functions with doubly occupied core orbitals to zero, thus effectively projecting them out of the wave function.…”

Section: Methodsmentioning

confidence: 99%

“…This strategy has been successfully used in the past to reproduce different types of Xray spectra, including metal L-edge, 37−40 K-pre-edge, 41,42 RIXS, 41,43 and Kα 44 and Kβ XES. 45 The 1s and 3p core-ionized states were calculated with a novel projection technique called the highly excited state (HEXS) 42,46,47 with doubly occupied core orbitals to zero, thus effectively projecting them out of the wave function.…”

Section: ■ Introductionmentioning

confidence: 99%

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Iron Kβ X-ray Emission Spectroscopy: The Origin of Spectral Features from Atomic to Molecular Systems Using Multi-configurational Calculations

Guo,

Braun,

Sokaras

et al. 2024

J. Phys. Chem. A

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Kβ X-ray emission spectroscopy (XES) is widely used to fingerprint the local spin of transition-metal ions, including in pump−probe experiments, to identify excited states or in chemical and biological reactions to characterize short-lived intermediates. In this study, the spectra of ferrous and ferric complexes for various spin states were measured experimentally and described theoretically through restricted active space (RAS) calculations including dynamic correlations. Through the RAS calculations from simple atomic models to complex molecular systems, spectral effects such as the exchange interactions, crystalfield strength, and covalent orbital mixing were evaluated and discussed. The calculations find that only the spectral features of low-spin cases show a dependence on the crystal-field strength, particularly for ferrous low spin. The effect of the covalent orbital mixing strength on the first moment of the Kβ 1,3 main line and the Kβ 1,3 −Kβ′ energy splitting is quantitatively described. Clear relationships are found within a given nominal spin but less between different spin states, which calls for careful selection of reference spectra in future experiments. This study further advances our understanding of the correlation between changes in experimental spectral features and their corresponding electronic structure information.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Iron Kβ X-ray Emission Spectroscopy: The Origin of Spectral Features from Atomic to Molecular Systems Using Multi-configurational Calculations

Guo,

Braun,

Sokaras

et al. 2024

J. Phys. Chem. A

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Ultrafast Two‐Color X‐Ray Emission Spectroscopy Reveals Excited State Landscape in a Base Metal Dyad

Nowakowski,

Huber‐Gedert,

Elgabarty

et al. 2024

Advanced Science

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Effective photoinduced charge transfer makes molecular bimetallic assemblies attractive for applications as active light‐induced proton reduction systems. Developing competitive base metal dyads is mandatory for a more sustainable future. However, the electron transfer mechanisms from the photosensitizer to the proton reduction catalyst in base metal dyads remain so far unexplored. A Fe─Co dyad that exhibits photocatalytic H2 production activity is studied using femtosecond X‐ray emission spectroscopy, complemented by ultrafast optical spectroscopy and theoretical time‐dependent DFT calculations, to understand the electronic and structural dynamics after photoexcitation and during the subsequent charge transfer process from the FeII photosensitizer to the cobaloxime catalyst. This novel approach enables the simultaneous measurement of the transient X‐ray emission at the iron and cobalt K‐edges in a two‐color experiment. With this methodology, the excited state dynamics are correlated to the electron transfer processes, and evidence of the Fe→Co electron transfer as an initial step of proton reduction activity is unraveled.

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Exploring the Influence of Approximations for Simulating Valence Excited X-ray Spectra

Penfold,

Curchod

2024

J. Phys. Chem. A

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First-principles simulations of excited-state X-ray spectra are becoming increasingly important to interpret the wealth of electronic and geometric information contained within femtosecond X-ray absorption spectra recorded at X-ray Free Electron Lasers (X-FELs). However, because the transition dipole matrix elements must be calculated between two excited states (i.e., the valence excited state and the final core excited state arising from the initial valence excited state) of very different energies, this can be challenging and time-consuming to compute. Herein using two molecules, protonated formaldimine and cyclobutanone, we assess the ability of n-electron valence-state perturbation theory (NEVPT2), equation-of-motion coupled-cluster theory (EOM-CCSD), linear-response time-dependent density functional theory (LR-TDDFT) and the maximum overlap method (MOM) to describe excited state X-ray spectra. Our study focuses in particular on the behavior of these methods away from the Franck−Condon geometry and in the vicinity of important topological features of excited-state potential energy surfaces, namely, conical intersections. We demonstrate that the primary feature of excited-state X-ray spectra is associated with the core electron filling the hole created by the initial valence excitation, a process that all of the methods can capture. Higher energy states are generally weaker, but importantly much more sensitive to the nature of the reference electronic wave function. As molecular structures evolve away from the Franck−Condon geometry, changes in the spectral shape closely follow the underlying valence excitation, highlighting the importance of accurately describing the initial valence excitation to simulate the excited-state X-ray absorption spectra.

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Sensitivity of Kβ mainline X-ray emission to structural dynamics in iron photosensitizer

Abstract: Photochemistry and photophysics processes involve structures far from equilibrium. In these reactions, there is often strong coupling between nuclear and electronic degrees of freedom. For first-row transition metals, Kβ X-ray...

Cited by 5 publications

References 94 publications

Iron Kβ X-ray Emission Spectroscopy: The Origin of Spectral Features from Atomic to Molecular Systems Using Multi-configurational Calculations

Iron Kβ X-ray Emission Spectroscopy: The Origin of Spectral Features from Atomic to Molecular Systems Using Multi-configurational Calculations

Ultrafast Two‐Color X‐Ray Emission Spectroscopy Reveals Excited State Landscape in a Base Metal Dyad

Exploring the Influence of Approximations for Simulating Valence Excited X-ray Spectra

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